Ring-shaped hydrofoil

ABSTRACT

A hydrofoil in the form of a short tubular ring or annular hydrofoil is disclosed for controlling the position of a connected tow cable below or to the side of a ship or other towing craft. An attached ballast weight and towing bridle are adjusted to maintain the desired attitute to the slip stream.

United States Patent [1 1 Gay, Jr. et al.

[ RING-SHAPED HYDROFOIL [75] Inventors: Shelton M. Gay, Jr., Vienna;

Frederick C. Belen, Jr., Arlington, both of Va.

[73] Assignee: The United States of America as represented by theSecretary of the Navy, Washington, DC.

[22] Filed: Oct. ll, 1973 [2]] App]. N0.: 405,358

[52] U.S. Cl 114/235 B [51] Int. Cl. B63B 21/56 [58] Field of Searchll4/235 R, 235 B, 66.5 H,

1l4/l6 F; 244/3, 34 A, l TD 56] References Cited UNITED STATES PATENTS2,325,616 8/l943 Landweber i. 114/235 B [111 3,893,403 [451 July 8,1975

3,012,534 l2/l96l Thomas ll4/235 R 3,l54,269 10/!964 Musil 244/34 A3,460,384 8/1969 Fohl r n 114/235 8 3,645,224 2/l972 Haberman ll4/235 BFOREIGN PATENTS OR APPLICATIONS 865,643 5/1940 France u 244/] TD PrimaryExaminer-Trygve M. Blix Assistant Examiner-Stuart M. Goldstein Attorney,Agent, or Firm-R. S. Sciascia; Q. E. Hodges; D. McGiehan [57] ABSTRACT Ahydrofoil in the form of a short tubular ring or annular hydrofoil isdisclosed for controiling the position of a connected tow cable below orto the side of a ship or other towing craft. An attached ballast weightand towing bridle are adjusted to maintain the desired atti tute to theslip stream.

2 Claims, 2 Drawing Figures 1 RING-SHAPED HYDROFOIL The inventiondescribed herein may be manufactured and used by or for the Governmentof the United States of America for governmental purposes without thepayment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The instant invention relates generally tohydrofoils such as paravanes or fish and more particularly to an annularring hydrofoil for depressing a towed cable.

Heretofore, typical methods for developing the forces required tomaintain a certain separation between a towing craft and the end of atow cable include conventional winged devices, buoyant floats, weights,and combinations thereof. In many applications it is desirable to towthe cable at some predetermined position below or to the side of theship or towing craft, and these applications require some dynamic liftbeyond mere static forces produced by simple buoyant and weight devices.

The conventional depressors, paravanes, otters or fish used to providelift are complex rectangular or tapered wing configurations withstabilizer surfaces, and require extensive structure support to sustainthe hydrodynamic loads. These complex configurations are highlysusceptible to damage during launching from an underway towing craft dueto the initial contact with the water and to the severe snatch-up loads.Another problem with these devices is that their behavior becomeserratic if the tow cable slacks during launch and even when the craft isunderway. Also initial high cost and the likelihood of damage aredisadvantages of the prior art devices.

SUMMARY OF THE INVENTION Accordingly, an object of the present inventionis to provide a new and improved towed cable controlling hydrofoil.

Another object of the instant invention is to provide a simple andreliable cable controlling hydrofoil that is relatively unsusceptible todamage.

Still another object of the present invention is to provide a cablecontrolling hydrofoil that is easy and safe to launch from a movingtowing craft.

A further object of the instant invention is to provide a cablecontroller that is free of erratic operation during cable slackness atlaunch and underway.

Briefly, these and other objects of the instant invention are attainedby the use of a hydrofoil having an annular ring or short tubeconfiguration which has an adjustable towing bridle and ballastingweight attached thereto. The bridle is adjusted to provide the desiredattitude of the ring hydrofoil with the slip stream to fly" down or tothe right or left. A ballasting weight is attached to the ring tomaintain the desired portion down and also to preclude rotation of thering.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of theinvention and many of the attendant advantages thereof will be readilyappreciated as the same becomes better understood by reference to thefollowing description when considered in connection with theaccompanying drawings wherein:

FIG. 1 is a pictorial view of towing craft with a towed cable controlledby the ring hydrofoil; and

FIG. 2 is a perspective view of the ring hydrofoil according to thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,wherein like reference numerals designate corresponding parts throughoutthe several views, there is shown generally in FIG. I a towing craft 10on the surface 12 of a body of water, towing cable 14, attached at itsdistal end to a ring hydrofoil 16. While the towing craft 10 is depictedas an aircraft such as a helicopter l flying in close proximity to thesurface, it is to be understood that it may be a surface ship, such as amine sweeper or a survey ship towing a hydrophone cable, a submarine orother submersible craft. Furthermore, the ring hydrofoil 16 may beplaced nearthe towing craft to depress or displace to the right or leftthe lead end of the cable 14. Also a buoy 18 on a pendant 20 shownattached to the ring hydrofoil I6 may be used to indicate its position.

Referring now to FIG. 2, the ring hydrofoil I6 is depicted in detail.The essential part is a short tubular ring or band 22 which may be ofany diameter necessary to produce the desired dynamic lift forces todepress or displace a towed cable, and made of steel, aluminum, plasticsor other suitable materials. The cross-section of the ring foil per seis shaped like an airfoil, having a blunt rounded leading edge 24 and atapered afterbody 26 ending in a sharp trailing edge 27, conducive tosmooth flow and dynamic lift. Attached to the hydrofoil ring near theleading edge thereof and generally diametrically opposed are a pair oflinks 28. Links 28 are attached to the ring for rotation at one end byconventional fasteners such as rivets or bolts. Connected between theother ends of the link is a bridle 30 of flexible cable material such asrope, wire rope, chain, or the like, depending on the strength required.At the center of the bridle 30 is a clamp-type connector 32 which may beslid along and clamped to the bridle for adjustment purposes, to bedescribed hereinafter. At the center of the connector 32 is an eye 34for attachment of the main tow cable 14. As shown and in operation, aballast weight 36 is secured to the lower portion of the ring byfasteners such as bolts, screws. rivets or the like. And although notalways necessary, a pair of trimming fins 38 may be affixed to the outerperiphery of the ring hydrofoil near the bridle links 28.

While the advantages and operation of the ringfoil may be obvious fromthe above description it will be further explained below. Obviously, aprimary advantage of the ringfoil lies in its simplicity of designmaking it singularly immune to damage as a result of striking object orduring launch. Depending on whether the device is to be used merely as acable depressor or to displace the cable to the left or right, thebridle links 28 may be placed near the leading edge 24 and at suchpositions around the ringfoil shown by experimentation and calculationto produce the desired result. Further, the bridle connector 32 may beadjusted along the bridle 30 to produce left or right lift, to displacethe cable to the side of the towing vessel. The tow cable 14 is attachedto the eye 34, and the rig launched in the usual manner.

The trimming fins 38 may be used to adjust the towing attitude in pitch,but are not required for stability as another feature of the ringhydrofoil is its inherent stability without these appendages. Typically,stability is defined in terms of various modes: pitch, roll, and yaw,and stabilization occurs when an excursion in a particular mode causes arestoring force to be generated. Therefore, perturbations from a pathresult in forces which restore the device to the path. If the ringfoil16 rolls, the low center of gravity produced by the ballast weight 36,and the relatively high bridle attachment results in a restoring moment.For pitch stability, a nose-up perturbation are restored by hydrodynamicgravity moments, by the ballast weight while a nosedown perturbation isrestored by hydrodynamic forces acting on the upper and lower surfacesof the foil 16. A perturbation in yaw is restored both by hydrodynamicforces on the ringfoil 16 as well as by the bridle 30. The bridleattachment is near the leading edge 24 of the foil to produce properclamping during operation.

Obviously many modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

l. A hydrofoil for controlling the depth and lateral displacement of acable being towed by a craft, comprising:

an annular ring having a thin radial cross section conducive to smoothflow and hydrodynamic lift presented edgewise to the slip stream havinga blunt rounded leading edge, a tapered afterbody, and a sharp trailingedge;

a bridle attached adjacent to the leading edge of said annular ring atsubstantially diametrically opposed positions;

a tow cable attached to said bridle intermediate the ends thereof; and

a ballast weight affixed to said annular ring.

2. The hydrofoil of claim 1 further comprising:

a ballast weight affixed to said annular ring at a lower and forwardposition concentrating the weight forward of said bridle attachment.

i i l

1. A HYDROFOIL FOR CONTROLLING THE DEPTH AND LATERAL DISPLACEMENT OF ACABLE BEING TOWED BY A CRAFT, COMPRISING: AN ANNULAR RING HAVING A THINRADIAL CROSS SECTION CONDUCIVE TO SMOOTH FLOW AND HYDRODYNAMIC LIFTPRESENTED EDGEWISE TO THE SLIP STREAM HAVING A BLUNT ROUNDED LEADINGEDGE, A TAPERED AFTERBODY, AND A SHARP TRAILING EDGE; A BRIDLE ATTACHEDADJACENT TO THE LEADING EDGE OF SAID ANNULAR RING AT SUBSTANTIALLYDIAMETRICALLY OPPOSED POSITIONS; A TOW CABLE ATTACHED TO SAID BRIDLEINTERMEDIATE THE ENDS THEREOF; AND A BALLAST WEIGHT AFFIXED TO SAIDANNULAR RING.
 2. The hydrofoil of claim 1 further comprising: a ballastweight affixed to said annular ring at a lower and forward positionconcentrating the weight forward of said bridle attachment.